1. Field of the Invention
The invention relates to a hinge device, more particularly to a hinge device for pivotally connecting two elements, such as a main body of a calculator and a lid for covering the main body.
2. Description of the Related Art
Referring to FIGS. 1 and 2, a conventional hinge device for pivotally connecting two elements is shown to comprise a first barrel 1, a second barrel 2, a pivot unit 3 and a plug member 4.
The first barrel 1 is fixed to one of the elements 92, such as a main body of a calculator, and has a first end 101, a second end 102 opposite to the first end 101, and a passage 10 which extends through the first barrel 1 with a first section 11 adjacent to the first end 101 and a second section 12 continuous with the first section 11 and adjacent to the second end 102. The second section 12 has a polygonal cross section which is narrower than that of the first section 11. The first section 11 is confined by a first inner surface , while the second section 12 is confined by a second inner surface which is integral with the first inner surface, thereby forming a shoulder 104 between the first and second sections 11, 12. The first barrel 1 further has a pair of opposed channels 105 which extend through the shoulder 104 substantially parallel to the first and second inner surfaces and which open to the first section 11 and the second end 12 of the first barrel 1.
The second barrel 2 is fixed to the other one of the elements, such as a lid 91, and has a front end 201, a rear end 202 opposite to the front end 201, and a passage 20 which extends therethrough with a front section 21 that is polygonal in cross section and that is located adjacent to the front end 201 and a rear section 22 continuous with the front section 21. The rear section 22 has a cross section smaller than that of the front section 21.
The pivot unit 3 includes a pin member 30, a hexagonal sleeve member 31 and a clip member. The pin member 30 has a front portion 34, a rear portion 33 opposite to the front portion 34 and an enlarged head 35 between the front and rear portions 33, 34. The enlarged head 35 has an external face corresponding to the front section 21 of the second barrel 2. The hexagonal sleeve member 31 has an external surface corresponding to the second section 12 of the first barrel 1.
The first and second barrels 1, 2 are disposed side by side such that the passages 10, 20 are in alignment. The pin member 30 is inserted into the first and second barrel 1,2 such that the enlarged head 35 is received engageably in the front section 21 of the second barrel 2, the front portion 34 extends into the first barrel 1 and such that a free end of the rear portion 33 of the pin member 30 extends beyond the rear section 22 of the second barrel 2. The clip member is constituted by a circumferential groove 332 formed on the rear portion 33 of the pin member 30 adjacent to the free end of the latter and a C-shaped snap ring 331 which is snap-fitted in the circumferential groove 332 so as to prevent the pin member 30 from disengaging the second barrel 2. The hexagonal sleeve member 31 is inserted into the first barrel 1 such that it sleeves around the front portion 34 of the pin member 30 and engages the second section 12 of the first barrel 1. The sleeve member 31 is provided with a central hole which has a diameter greater than that of the front portion 34 of the pin member 30 so that a clearance is formed between the front portion 34 of the pin member 30 and an inner surface that confines the central hole of the sleeve member 31. A friction ring 32, generally made of plastic, is inserted into the clearance to provide friction when the sleeve member 31 is rotated relative to the front portion 34 of the pin member 30.
The plug member 4 has two hooked ribs 40 and is inserted into the first barrel 1 via the first end 101 such that the plug member 4 abuts the first end 101 of the first barrel 1 and a distal end of the front portion of the pin member 30 while the hooked ribs 40 pass through the first section 10 and the channels 105 of the first barrel 1 and engage the periphery that confines the second end 102 of the first barrel 1. Under this condition, the pin member 30 is retained within the first and second barrel 1, 2 and correspondingly prevents the first and second barrels 1, 2 from disengaging one another.
Some of the disadvantages that result with the use of the conventional hinge device are:
(I) The pivot unit 3 is constituted by three components, i.e. the pin member 30, the sleeve member 31 and the friction ring 32. Thus, a longer time and extra expense are incurred when producing.
(II) It is difficult to insert the friction ring 32 into the clearance which is formed between the inner surface of the sleeve member 31 and the front portion 34 of the pin member 30 after the pin member 30 and the sleeve member 31 have been assembled in the first and second barrel 1, 2.